Thread:Sweetangel823/@comment-30038526-20180318222540/@comment-17703532-20180318223322

That's kinda' the thing about the 154.5th generation, and it has to do with the lore we came up with to explain new members coming along outside of audition times.

The basic story regarding the 154.5th generation is that during the 154th generation audition, there were a lot of members who for reasons (DES, etc) were unable to attend the second round of the auditions. After getting approached by Karin and Aoi, the management decided to open auditions for the 154.5th generation - but only to those who passed the first round of the 154th generation but were unable to reach the second.

That kind of means that there is no set center or designated "first stage", because new members can keep coming at basically any time; Karin and Aoi debuted before they were "complete" members of 00, and Mayu, Yuuri and Ayaka debuted after that